Method For Optimizing Aircraft Landing On A Runway

ABSTRACT

According to the invention, a target vertical speed (Vzo), defined in relation to the ground, is determined and an optimized ground slope (γ o ), associated with an approach path (A) to keep track during the landing, is determined on the basis of said determined target vertical speed (Vzo) and of at least one outside parameter, said optimized ground slope) (γ o ) being at least equal to a predetermined ground slope (γ i ).

The present invention relates to a method for optimizing the landing ofan aircraft on a runway, as well as a corresponding optimization device.

As known, according to standard procedure rules, an aircraft (forinstance a civil transport airplane) switches from a descent startaltitude to a final approach start altitude:

-   -   either while carrying out a descent at a constant speed,        followed by a defined approach level, for instance, by an        altitude of 3,000 feet (that is about 914 meters), for        decelerating and then stabilizing at a predetermined        intermediary speed, the aircraft maintaining this level, with        this intermediary speed, until it intercepts a predefined final        approach path;    -   while carrying out a continuous descent approach, wherein the        deceleration level at a constant altitude is omitted, so that        the aircraft descends and decelerates simultaneously, this step        being optimally divided into several sections each having        specific descent slopes.

Intercepting the approach level, or the last segment of the approach ina continuous descent, and the approach path defines the initiation ofthe final approach phase.

The standard slope associated with this approach path and defined inrelation to the ground (the reason why it will be referred to as<<ground slope>> later on) is usually set at −3°. During the approachphase, the aircraft decelerates again, keeping track of the approachpath, while spreading the slats, the flaps and the landing gears, so asto exhibit a landing configuration. At approximately 1000 feet (that isabout 305 meters), the aircraft keeps a stabilized approach at apredefined approach speed (being, more specifically, a function of theconfiguration of the aircraft and of the meteorological conditions) upto 50 feet (that is about 15 meters), and then initiates its flare so asto join the runway and complete the landing.

It is known as well that, in order to avoid obstacles (for instanceformed by the relief, buildings, etc.), an increased ground slopeapproach phase (that is for instance, switching from a −3° standardground slope to a −4° ground slope) could be carried out. It should benoticed that, whatever the final ground slope to track, the latter ispublished in the operational approach procedures as defined by the airauthorities.

It is also known that, in addition to air safety considerations, anincreased ground slope approach phase enables to reduce theenvironmental impacts in the vicinity of airports (including noise andpolluting emissions), as, thru the geometric structure, the aircraftflies higher for a same distance to the threshold of the runway and thatthe motor speed necessary to maintain this slope is lower in general.This explains why the different actors of the aeronautic field (aircraftmanufacturers, airports, air companies) are eager to develop increasedground slope approaches.

Furthermore, it is known that transport civil dedicated aircraftsgenerally carry out their final approach on a ground slope set at −3°,while being certified for flying up to −4.49° ground slopes. Beyond thisslope value, the approach phase is considered, by the internationalrules, as an approach on a steep slope and the aircraft should suitadditional certification requirements.

Although such increased ground slopes (that is higher than −3° but lowerthan −4.5°) are regularly followed on numerous international airports,in order to avoid obstacles, it is not usual for the aircraft to landabruptly (this is referred to, in such a case, as a <<hard>> landing),being able to compromise the good behaviour of the aircraft, includingwhen such hard landings are daily occurring.

In other words, in order to stand up to regular increased ground slopeapproaches (equal for instance to −4°), it is indispensable to reviewthe design criteria of the aircraft in terms of performance,maneuverability, or even of structure, so as to ensure a securedlanding, whatever the characteristics of the aircraft, themeteorological conditions and the geographical situations in thevicinity of airports.

Indeed, increasing the ground slope during a final approach results, onthe one hand, in an increase of the vertical speed of the aircraft inrelation to the ground (also referred to as <<ground vertical speed>>subsequently) and, on the other hand, in a decrease of the decelerationabilities of the aircraft (at the origin of hard landings). It can, forinstance, be shown that, in the case of a conventional speed Vgs, a −1°increase of a ground slope initially at −3° (that is an increased groundslope equal to) −4° could result in the vertical speed Vz increasing bymore than 30%.

An increase of the ground slope (and thus of the vertical ground speed)involves a review of maneuverability and deceleration abilities, evenredimensioning landing gears, resulting in an additional embedded load,important modifications of the systems of the aircraft, as well as theneed of an adapted training of pilots.

The present invention aims at solving these drawbacks.

To this end, according to this invention, the method for optimizing thelanding of an aircraft on a runway, said landing comprising an approachphase, defined by an approach path to be tracked with which a predefinedground slope is associated, and a flaring phase, is remarkable in that:

-   -   in a preliminary step:    -   a target vertical speed in relation to the ground to be applied        to said aircraft upon the initiation of the flaring phase is        defined on the basis of performances and characteristics        specific to said aircraft; and    -   as a function of said target vertical speed and of at least one        outside parameter, an optimized ground slope, associated with        the approach path, is determined which is higher than or equal        to the predetermined ground slope, and    -   as soon as the approach path is intercepted by the aircraft,        said aircraft is guided so as to track the determined optimized        ground slope, associated with said approach path, and to reach        the previously defined target vertical speed at the initiation        of the flaring phase.

Thus, thanks to this invention, the ground slope of the approach path isoptimized, during the approach phase, while determining an optimizedground slope (with respect to the ground slope issued from standardprocedure rules) from a target vertical speed predefined, based oncharacteristics being specific to the aircraft and one or more outsideparameters, such as those associated with meteorological conditions,environmental conditions and characteristics specific to the aircraft.

Indeed, it has been shown that the flare carried out upon a landing ofan aircraft depends nearly exclusively on the ground vertical speed ofthe aircraft, so that is forms an efficient parameter for characterizingthe flare and provides an indication on the ability of the aircraft toensure a secured landing and to avoid an inappropriately throttling up.The present invention is advantageously based on the fact that the abovementioned outside parameters disturb the deceleration abilities of theaircraft, at a set ground slope, and increase the risk that the aircraftshould abruptly land on the runway, so that taking the latter intoconsideration in the calculation of the optimized ground slope enablesto reduce the risk of hard landings.

In other words, setting the ground vertical speed of the aircraft uponthe initiation of the flare (at about 50 feet) to a preliminarilydefined nominal target value, the present invention will secure thefinal approach phase, providing a more constant, repeated and easierflare, while increasing the slope, making advantageously use of theconditions of the approach being considered for improving theenvironmental aspects, without imposing new designing constraints.

The higher the ground slope of the approach, the lower the motor speedof the aircraft along the approach path, reducing the atmospheric andsound pollution, as well as the fuel consumption of the aircraft.

In addition, the optimizing method of the present invention also has theadvantage of being able to be implemented:

-   -   readily in any aircraft;    -   without any structural modification of the aircraft;    -   without modification of the piloting laws or of the aerodynamic        configuration of the aircraft;    -   without modification of operational procedures;    -   without impact on the air traffic control;    -   without modification of the airport facilities on the ground;        and    -   without additional certification specific to this concept.

Preferably, the outside parameter(s) belong to the group of parameterscomprising:

-   -   the calibrated airspeed CAS of the aircraft with respect to the        air. This speed CAS is a function of the bulk of the aircraft        and of the flight configuration of the aircraft associated with        the approach phase, so that, involving the speed CAS in the        determination of the optimized slope, these last two parameters        (bulk M, flight configuration) are taken into consideration;    -   the outside temperature at a standard height;    -   the horizontal speed of the wind;    -   the inclination of the runway with respect to the horizontal;        and    -   the altitude of the runway.    -   Preferably, the optimized ground slope is determined from the        target vertical speed, the calibrated airspeed CAS, the        horizontal speed of the wind, the outside temperature at a        standard height, as well as from the inclination and the        altitude of the runway.

In addition, the horizontal speed of the wind, taken into considerationduring the determination of the optimized ground slope, belongs to adetermined range of values able to be obtained from severaltechnological solutions.

Furthermore, for determining the optimized ground slope preferably thefollowing steps are carried out:

-   -   the density of the air at the standard height is determined from        the outside temperature and from the altitude of the runway;    -   the true speed TAS of the aircraft with respect to the air is        determined from the speed CAS and from the determined density of        the air;    -   the optimized ground slope is determined from the target        vertical speed, from the determined true speed TAS, from the        horizontal speed of the wind and from the inclination of the        runway.

In a particular embodiment, the determination of the optimized groundslope is obtained thru geometric construction of a speed triangle.

Moreover, the target vertical speed could be defined preliminarily foreach type of aircraft.

So as not to decrease the safety margins imposed by the air safetyauthorities, the optimized ground slope ranges between a predefinedlower extreme value and a predefined higher extreme value, preferablyequal respectively to −3° and to −4.49°.

Furthermore, the horizontal speed of the wind could be obtainedaccording to at least one of the following ways:

-   -   thru measurement of the wind at the level of the control tower        of the runway being considered, without taking gusts into        consideration;    -   thru retrieving data measured directly by one or more other        aircrafts located in the vicinity of the runway.

The present invention further relates to a device for optimizing thelanding of an aircraft on a runway, said landing comprising an approachphase, defined by an approach path to be tracked with which a predefinedground slope is associated, and a flaring phase. According to thisinvention, such a device comprises:

-   -   means for determining, as a function of at least one outside        parameter and of a target vertical speed, preliminarily defined        from performances and characteristics being specific to said        aircraft, an optimized ground slope associated with the approach        path to be tracked being higher than or equal to the predefined        ground slope; and    -   means for guiding the aircraft as soon as the latter intercepts        the approach path, so that it can track the determined optimized        ground slope associated with said approach path, and it reaches        the preliminarily defined target vertical speed during the        initiation of the flaring phase.

Moreover, as the optimized ground slope is determined from said targetvertical speed, the calibrated airspeed CAS, the horizontal speed of thewind, the outside temperature at a standard height, as well as theinclination and the altitude of the runway, said determination meanspreferably comprise:

-   -   means for calculating the density of the air at the standard        height as a function of the outside temperature and of the        altitude of the runway;    -   means for calculating the true speed TAS of the aircraft with        respect to the air from the speed CAS and from the determined        density of the air; and    -   means for calculating the optimized ground slope from the target        vertical speed, from the determined true speed TAS, from the        horizontal speed of the wind and from the inclination of the        runway.

Furthermore, the present invention further relates to an aircraftcomprising a device such as specified hereinabove.

The FIGS. of the appended drawing will better explain how this inventioncan be implemented. In these FIGS., like reference numerals relate tolike components

FIG. 1 represents a diagram showing the method according to the presentinvention.

FIGS. 2 to 4 each represent a speed triangle allowing for geometricallydetermining the optimized slope according to this invention, in the caseof a lack of wind, of a back wind and of a front wind, respectively.

FIG. 5 is a block diagram of a device for implementing the methodaccording to this invention.

In the situation schematically shown on FIG. 1, an aircraft AC is in anapproach phase, with the aim to land on a runway 2 located at analtitude Zp. After a flight on the altitude approach level Za or after acontinuous descent intermediary approach, the aircraft AC intercepts afinal approach path A, having an optimized ground slope γ_(o) determinedas described subsequently, at point Pa (corresponding to theintersection of the level Za, or of the continuous descent approachsegment, and of the approach path A) and descends along said axis A inthe direction to the runway 2 so as to decelerate until a stabilizedapproach speed Vapp at a stabilization altitude Zs at about 1000feet(point Ps) for reaching afterwards the target vertical speed Vzo inrelation to the ground 3 being constant at point Po. The latterindicates the start of the flare 4 following the approach phase.

As shown on FIG. 1, the optimized ground slope γ_(o) is higher than theinitial ground slope γ_(i) (for instance γ_(i)=−3° and γ_(o)=−4°) beingdetermined by standard procedure rules.

Preferably, the optimized ground slope γ_(o) ranges between a lowerextreme value (for instance equal to −3°) and a higher extreme value,(for instance equal to −4.49°), so as not to decrease the safety marginsimposed by the air authorities.

According to the present invention, in order to optimize the landing ofthe aircraft AC on the runway 2, first:

-   -   a target vertical speed Vzo is defined in relation to the ground        3 to be applied to the aircraft AC upon the initiation of the        flare. Such a vertical ground speed Vzo is defined from        performance and characteristics being specific to the aircraft,        for instance thru simulations carrying out performance and        robustness calculations. The definition of Vzo results from an        acceptable compromise between the safety relating to the flare 4        and the reduction of the (sound and atmospheric) pollution and        of the fuel consumption. In the remainder, it is considered that        Vzo is independent from the embedded bulk of the aircraft AC, so        that Vzo is identical whatever the embedded bulk. Alternatively,        it could be contemplated that Vzo depends on the bulk embedded        on-board the aircraft, so that Vzo could be determined from        embedded bulk/speed Vzo abacuses; and    -   the optimized ground slope γ_(o) associated with the approach        path A is determined from the target vertical speed Vzo and from        outside parameters as detailed hereinafter.

Subsequently, <<outside parameters>> refer to the parameters associatedwith the meteorological conditions, the environmental conditions and thecharacteristics specific to the aircraft AC.

In particular, outside parameters able to be involved in determining theoptimized ground slope according to this invention include:

-   -   the calibrated airspeed CAS of the aircraft AC with respect to        the air; This speed CAS is a function of the bulk M of the        aircraft and the flight configuration of the aircraft AC        associated with the approach phase. Otherwise stated, using the        speed CAS, the bulk M and the flight configuration of the        aircraft AC are indirectly taken into consideration. It should        further be noticed that the higher the bulk of the aircraft AC        upon landing, the higher too the over-all approach speed,        resulting in the ground slope decreasing, associated with the        axis A at the vertical iso speed Vz and conversely;    -   the outside temperature To at a standard height ho (for instance        equal to 50 feet). The temperature T of the ambient air act on        the tracked ground slope associated with the axis A to the        vertical iso speed. If the temperature T is lower than the        standard temperature To defined at destination, the tracked        ground slope will be finally higher than the initial ground        slope γ_(i) and conversely for higher temperatures;    -   the altitude Zp of the runway 2. Indeed, the density of the air        varies as a function of the altitude of the runway Zp, so that        the latter acts directly on the true speed TAS of the aircraft        with respect to the air. Thus, the higher the altitude Zp of the        airport, the lower the density of the air, so that the more the        true speed TAS increases and the tracked ground slope is gentle;    -   the inclination γ_(P) of the runway 2 when it is available in        the navigation base. The optimized ground slope γ_(o) is        directly corrected from this inclination γ_(P), for instance        through geometric construction; and    -   the horizontal speed of the wind Vw being one of the most        influent available parameters in the relationship linking the        ground vertical speed of the aircraft and the ground slope        associated with the approach path A. When the ground vertical        speed Vz of the aircraft AC is set, a front wind easily and        instantaneously allows flying along the approach path A with an        increased ground slope at iso air slope. The horizontal speed of        the wind Vw, used for determining the optimized ground slope        according to the method of this invention, could be obtained        according to at least one of the following ways:    -   thru measurement of the wind at the level of the control tower        of the runway 2 without taking gusts into consideration; and/or    -   thru retrieval of data measured by one or more other aircrafts        located in the surrounding of the track 2 and transmitted        directly to the aircraft AC.

Several methods for obtaining the horizontal speed of the wind Vw couldbe used simultaneously for minimizing error measurements. Moreover, adetermined range of speed values VW could be defined, to be taken intoconsideration upon determining the optimized ground slope γ_(o). Inorder to maintain some safety margin, only part of the wind could betaken into consideration. For instance, up to 15 kts of front wind, 80%of the wind could be considered. For stronger winds (the speed Vw ofwhich is higher than 15 kts), a lower consideration of the wind could beimplemented. Theoretically, the method of this invention enables toachieve a final approach at iso thrust, iso attitude of the aircraft ACand iso vertical speed Vz, whatever the horizontal speed of the wind Vw.

According to this invention, for determining the optimized ground slopeγ_(o), the following steps are carried out:

-   -   the density of the air (ρ_(c)) at the standard height ho is        determined from the outside temperature To and from the altitude        of the runway Zp. More precisely, from the altitude of the        runway Zp, the atmospheric pressure P is deduced at the altitude        Zp, allowing to calculate the density of the air ρ_(c) at the        standard height ho thru the relationship

${\rho_{c} = \frac{P}{R \cdot {To}}},$

where R=287.053 J/kg/m³.

-   -   the true speed TAS of the aircraft is determined with respect to        the air from the speed CAS.

To this end, the calibrated airspeed CAS is retrieved, corresponding tothe approach speed being considered. This value is for instanceavailable from the FMS (for Flight Management System). Afterwards, thetrue speed TAS is determined thru the relationship

${{TAS} = {\sqrt{\frac{\rho_{c}}{\rho_{o}}} \cdot K \cdot {CAS}}},$

where ρ_(o)=1.225 kg/m³ and K is a coefficient of compressibilitycorrection; and

-   -   optimized ground slope (γ_(o)) is determined from the target        vertical speed Vzo, from the determined true speed TAS, from the        horizontal speed of the wind Vw and from the inclination of the        runway (γ_(P)). Such a determination could be obtained in a        simplified way thru geometric construction of a speed triangle.        Indeed, as shown on FIGS. 3 to 5 (on which the inclination of        the runway is nil) presenting respectively the case where there        is no wind (Vw=0, FIG. 2), the case where there is some back        wind (Vw>0, FIG. 3) and the case where there is a front wind        (Vw<0, FIG. 4), thru building a speed triangle from the        determined speed TAS and the constant target vertical speed Vzo,        the optimized ground slope γ_(o) is obtained. During the absence        of wind (FIG. 2), the speed of the aircraft AC in relation to        the ground Vgs is equal to the speed TAS (that is TAS=Vgs). In        the case of a back wind (FIG. 3), the speed Vgs is higher than        the speed TAS (that is TAS<Vgs) and γ_(o) is less high than that        obtained in the absence of wind. In the case of a front wind        (FIG. 4), the speed Vgs is lower than the speed TAS (that is        TAS>Vgs) and γ_(o) is higher than that obtained in the absence        of wind.

Thus, after determining the optimized ground slope γ_(o) in the abovementioned way, upon the interception by the aircraft AC of the approachpath A at point Pa, the aircraft AC is guided so that it tracks theoptimized ground slope γ_(o) associated with the approach path A, and itreaches the target vertical speed Vzo upon the initiation of the flaringphase 4 (point Po).

For determining the optimized ground slope γ_(o) and guiding theaircraft AC as mentioned hereinabove, the device 5 illustrated on FIG. 5could be used. It comprises:

-   -   means 6 for determining the optimized ground slope γ_(o),        associated with the approach path A to be tracked, receiving the        outside temperature To at a standard height ho, the inclination        γ_(P) and the altitude Zp of the runway 2, the calibrated        airspeed CAS, the target vertical speed Vzo and the horizontal        speed of the wind Vw; and    -   means 7 for guiding the aircraft upon the interception (point        Pa) by the latter of the approach path A, for imposing to it to        track the associated optimized slope γ_(o) and have it reach the        target vertical speed Vzo at point Po.

The determination means 6 comprise:

-   -   means 8 for calculating the density of the air ρ_(c) at the        standard height ho as defined hereinabove. They receive the        outside temperature To and the altitude of the runway Zp, via        links L1 and L2. The means 8 are able to deliver, in outlet, the        density of the air ρ_(c) at the height ho;    -   means 9 for calculating the true speed TAS of the aircraft AC as        set forth previously. They receive the density of the air ρ_(c)        as determined by the means 8 and the calibrated airspeed CAS,        via links L3 and L4. The means 9 are able to deliver, in outlet,        the true speed TAS; and    -   means 10 for calculating the optimized ground slope γ_(o) as        mentioned hereinabove. They receive the true speed TAS        determined by the means 9, the target vertical speed Vzo, the        horizontal speed of the wind Vw, as well as the inclination of        the runway γ_(P) via links L5, L6, L7 and L9. They are able to        deliver, in outlet, the optimized ground slope γ_(o) so that it        could be processed by the guiding means 7.

The means 6 for determining the optimized slope γ_(o) could be integralwith the flight management system FMS or with another embedded system inconnection with the flight management system. Alternatively, they couldbe outside the aircraft and have the form of a laptop or be evenintegrated into a station on the ground able to communicate theoptimized slope γ_(o) to the aircraft AC. The optimized slope γ_(o)could be transmitted from the determination means 6 to the FMS, or evenbe entered manually in the FMS by pilots.

Moreover, the guiding means 7 comprise the following means (not shown onthe Figs.):

-   -   a calculation means being intended for determining, usually,        piloting instructions from information received from the        determination means 6 via the link L8;    -   at least one means for aiding piloting, for example, an        automatic piloting device and/or a flight director, determining,        from the piloting instructions received from said calculation        means, piloting instructions of the aircraft AC; and    -   means for actuating controlled organs, such as for instance        (direction, depth) control surfaces of the aircraft, to which        the thus determined piloting instructions are applied.

Furthermore, it could be contemplated that the determination of theoptimized ground slope γ_(o) and guiding the aircraft along the axis Awith a slope γ_(o) are optional, providing activation and deactivationfunctions of such operations as, for instance, an activation meansintegrated into the cockpit of the aircraft AC.

In addition, it could also be provided that an indication should bedisplayed inside the cockpit (for instance) as a visual signal fornotifying the pilots that the method for optimizing the landingaccording to this invention is activated. Thereby, pilots will not besurprised by a later interception of the increased slope approach path Awith respect to that relating to conventional approaches (ground slopeequal to −3°).

1. A method for optimizing the landing of an aircraft (AC) on a runway(2), said landing comprising an approach phase, defined by an approachpath (A) to be tracked with which there is associated a predefinedground slope (γ_(i)), and a flaring phase (4), wherein: in a preliminarystep: a target vertical speed (Vzo) in relation to the ground (Vzo) tobe applied to said aircraft upon the initiation of the flaring phase (4)is defined on the basis of performances and characteristics beingspecific to said aircraft (AC); and as a function of said targetvertical speed (Vzo) and of at least one outside parameter, an optimizedground slope (γ_(o)), associated with the approach path (A), isdetermined, which is higher than or equal to the predetermined groundslope, and upon the interception by the aircraft (AC) of the approachpath (A), said aircraft (AC) is guided so as to track the determinedoptimized ground slope (γ_(o)), associated with said approach path (A),and to reach the preliminarily defined target vertical speed (Vzo) uponthe initiation of the flaring phase (4).
 2. The method according toclaim 1, wherein said outside parameter belongs to the group ofparameters comprising: the calibrated airspeed (CAS) of the aircraft(AC) with respect to the air; the outside temperature (To) at a standardheight (ho); the horizontal speed of the wind (Vw); the inclination ofthe runway (2) with respect to the horizontal; and the altitude (Zp) ofthe runway (2).
 3. The method according to claim 1, wherein theoptimized ground slope (γ_(o)) is determined from the target verticalspeed (Vzo), the calibrated airspeed (CAS), the horizontal speed of thewind (Vw), the outside temperature (To) at the standard height (ho), aswell as from the inclination (γ_(P)) and from the altitude (Zp) of therunway (2).
 4. The method according to claim 1, wherein the horizontalspeed of the wind (Vw), taken into consideration during thedetermination of the optimized ground slope (γ_(o)), belongs to adetermined range of values.
 5. The method according to claim 3, wherein,for determining the optimized ground slope, the following steps arecarried out: the density of the air (ρ_(c)) at the standard height (ho)is determined from the outside temperature (To) and from the altitude(Zp) of the runway; the true speed (TAS) of the aircraft with respect tothe air is determined from the speed (CAS) and from the determineddensity of the air (ρ_(c)); and the optimized ground slope (γ_(o)) isdetermined from the target vertical speed (Vzo), from the determinedtrue speed (TAS), from the horizontal speed of the wind (Vw) and fromthe inclination (γ_(P)) of the runway.
 6. The method according to claim1, wherein the determination of the optimized ground slope (γ_(o)) isobtained thru geometric construction of a speed triangle.
 7. The methodaccording to claim 1, wherein the target vertical speed (Vzo) ispreliminarily defined for each type of aircraft.
 8. The method accordingto claim 1, wherein the optimized ground slope (γ_(o)) ranges between apredefined lower extreme value and a predefined higher extreme value,preferably equal respectively to −3° and to −4.49°.
 9. A device foroptimizing the landing of an aircraft (AC) on a runway (2), said landingcomprising an approach phase, defined by an approach path (A) to betracked with which there is associated a predefined ground slope(γ_(i)), and a flaring phase (4), wherein it comprises: means (6) fordetermining, as a function of at least one outside parameter and atarget vertical speed (Vzo) preliminarily defined from performances andfrom characteristics being specific to said aircraft (AC), an optimizedground slope (γ_(o)) associated with the approach path (A) to be trackedbeing higher than or equal to the predefined ground slope (γ_(i)); andmeans (7) for guiding the aircraft (AC) upon the interception of theapproach path (A) by the latter, so that it tracks the determinedoptimized ground slope (γ_(o)), associated with to said approach path(A), and it reaches the preliminarily defined target vertical speed(Vzo) upon the initiation of the flaring phase (4).
 10. The deviceaccording to claim 9, wherein, the optimized ground slope (γ_(o)) beingdetermined from said target vertical speed (Vzo), the calibratedairspeed (CAS), the horizontal speed of the wind (Vw), the outsidetemperature (To) at the standard height (ho), as well as from theinclination (γ_(P)) and from the altitude (Zp) of the runway (2), saiddetermination means (6) further comprise: means (8) for calculating thedensity of the air (ρ_(c)) at the standard height (ho) as a function ofthe outside temperature (To) and of the altitude of the runway (Zp);means (9) for calculating the true speed (TAS) of the aircraft withrespect to the air from the speed (CAS) and the determined air density(ρ_(c)); and means (10) for calculating the optimized ground slope(γ_(c)) from the target vertical speed (Vzo), from the determined truespeed (TAS), from the horizontal speed of the wind (Vw) and from theinclination (γ_(P)) of the runway.
 11. An aircraft, wherein it comprisesa device (5) such as specified in claim 9.